Nadežda Talijan

Comparison of properties of silver-metal oxide electrical contact materials

Changes in physical properties such as density, porosity, hardness and electrical conductivity of the Ag-SnO2 and Ag-SnO2In2O3 electrical contact materials induced by introduction of metal oxide nanoparticles were investigated. Properties of the obtained silver-metal oxide nanoparticle composites are discussed and presented in comparison to their counterparts with the micro metal oxide particles as well as comparable Ag-SnO2WO3 and Ag-ZnO contact materials. Studied silvermetal oxide composites were produced by powder metallurgy method from very fine pure silver and micro- and nanoparticle metal oxide powders. Very uniform microstructures were obtained for all investigated composites and they exhibited physical properties that are comparable with relevant properties of equivalent commercial silver based electrical contact materials. Both Ag-SnO2 and Ag- SnO2In2O3 composites with metal oxide nanoparticles were found to have lower porosity, higher density and hardness than their respective counterparts which can be attributed to better dispersion hardening i.e. higher degree of dispersion of metal oxide in silver matrix.

Calorimetric study and phase diagram investigation of the Au–Ga system

Abstract The results of calorimetric study and phase equilibria investigation of the Au–Ga system, in the Ga-rich region, are presented. Calorimetric study was done using Oelsen methodology and partial and integral molar thermodynamic quantities were determined at a temperature of 873 K. Phase equilibria investigations were done experimentally – using differential thermal analysis, light optical microscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy, and theoretically – using the CALPHAD method. Results agree well with available literature data.

Phase diagram investigation of the Sn-InxAgyCuz (x:y:z = 7:2:1) section in the Ag-In-Sn-Cu system

Abstract The results of phase diagram investigation and characterization of the Ag-In-Sn-Cu system are presented in this paper. Samples at the In : Ag : Cu = 7 : 2 : 1 vertical section were measured with differential scanning calorimetry, and the obtained transition temperatures were compared with calculated values. From Calphad-type calculation, the phase diagram for Sn-InxAgyCuz (molar ratio x:y:z = 7:2:1) section is constructed. In order to obtain the microstructure of investigated alloys, scanning electron microscopy with energy dispersive X-ray spectroscopy was used.

Characterization of Au-Ga Alloys with Low Gold Content

Abstract The results of an experimental investigation of structural, mechanical and electrical characteristics of the alloys in Au-Ga system are presented in this paper. Selected alloys AuxGay (x = 0.1 — 0.3) were examined using light microscopy and SEM-EDX analysis as well as hardness, microhardness and electroconductivity measurements.

Experimental investigation and thermodynamic prediction of the Ga–Sb–Sn phase equilibria

Abstract Optimized thermodynamic data, successfully used for phase diagram calculations of constitutive binary systems, were used for prediction of phase equilibria in the ternary Ga–Sb–Sn system. The projection of the liquidus surface, invariant equilibria and three vertical sections with molar ratios Sb:Sn = 1, Ga:Sn = 1 and Ga:Sb = 1 of the Ga–Sb–Sn ternary system were calculated using the CALPHAD method. Alloys, situated along three selected vertical sections, were investigated using differential scanning calorimetry. The experimental phase equilibria data from this work and literature were compared with calculation results.

Ternary Bi-Cu-Ni alloys – thermodynamics, characterization, mechanical and electrical properties

The Bi–Cu–Ni ternary system belongs to the group of potential Cu-Ni-based advanced lead-free solder materials for high temperature application. The paper shows results of the thermodynamic calculations using general solution model along the line with the molar ratio of Cu: Ni = 1:1. The experimental part shows thermal, structural, electrical and mechanical properties based on differential scanning calorimetry (DSC), scanning electron microscopy with energy dispersive spectrometry (SEM-EDS), electroconductivity and hardness measurements of the alloys selected in the section from bismuth corner with molar ratio Cu: Ni = 1:1, Cu: Ni = 3:1, and Cu: Ni = 1:3.

Professor Dr. Dragana T. Živković – biography

On 26 November 2016, Professor dr DRAGANA ŽIVKOVIC passed away. She was a full-time professor and Dean of the Technical Faculty in Bor, University of Belgrade, Editor-in-Chief of the Journal of Mining and Metallurgy, Section B-Metallurgy, as well as the Founder and Chairman of the Committee for Thermodynamics and Phase Diagrams of Serbia.

EFECTS OF CHEMICAL COMPOSITION ON THE MICROSTRUCTURE AND PROPERTIES OF THE CU-Ge-Sb ALLOYS

In the current study a ternary Cu-Ge-Sb system has been experimentally assessed. Chemical and phase compositions of the alloy samples from three vertical sections Cu-GeSb, Ge-CuSb and Sb- CuGe were studied using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) and confirmed by X-ray diffraction analysis (XRD). Hardness of the alloys was measured by Brinell method while hardness of phases was measured using micro Vickers method. Electrical conductivity of the studied alloys was measured using eddy current instrument. Based on experimentally determined values iso-lines of hardness and electrical conductivity for the whole ternary system were calculated using assumed mathematical models.

Effect of chemical composition on microstructure, hardness and electrical conductivity profiles of the Bi-Cu-Ga alloys at 100 °C

Theoretical calculation and experimental investigation of the isothermal section of a ternary Bi-Cu-Ga system at 100 oC are presented in this paper. Thermodynamic binary-based calculation of the isothermal section was performed using Pandat software. Experimental investigation included microstructural analysis carried out using light optical microscopy (LOM) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), phase composition analysis using X-ray diffraction (XRD), Brinell and Vickers hardness testing and electrical conductivity measurements. In total, thirty alloy samples with compositions along three vertical sections Bi-CuGa, Cu-BiGa and Ga-BiCu were studied. The obtained experimental results support the calculated phase regions of the isothermal section at 100 oC. Hardness of individual phases as well as hardness and electrical conductivity of the studied alloys were measured. Based on the experimentally obtained results iso-lines of Brinell hardness and electrical conductivity along the whole compositional range were calculated by using appropriate mathematical models.

Phase Equilibria Calculation and Investigation of Hardness and Electrical Conductivity for Alloys in Selected Sections of Bi-Cu-Ni System

The results of phase equilibria calculation and the experimental investigation of alloys in selected sections of Bi-Cu-Ni system with bismuth constant molar content of 0.6; 0.7; 0.8; and 0.9 are presented in this paper. Thermodynamic calculation was done according to the CALPHAD method using PANDAT software, while chosen alloys in the selected sections were experimentally investigated using hardness and electrical conductivity measurements.